Mike is the Nick Carraway of Planet Doonesbury. As Nick both observed and indulged (a little) in the riotous goings-on next door at Jay Gatsby's, Mike stands both with and apart from his nutty friends. Zonker, B.D., and (especially) Duke are cartoons, but Mike is so sane that he scarcely belongs in a comic strip. He is, as Trudeau writes in the character sketch about Mike, "the group's designated grown-up."
And that, of course, is what makes Mike indispensable—and a clue to the enduring appeal of Doonesbury as a whole. It's only a minor overstatement to say that Trudeau's strip provides a comprehensive history of the past 40 years. Reading through this collection (which is easier than lifting it), we see that Trudeau has his enduring obsessions—Vietnam, for starters—but every trend, inanity, and insanity of recent American history has gotten the once-over in the strip. Safe sex to global warming, virtual reality to reality TV—it's all there. (Even NAFTA, for God's sake.) But Trudeau isn't just trend-surfing popular and political culture; he's got a real, sometimes fierce, point of view on it all.
Consider the defining Mike Doonesbury moment: his advertising campaign for R.J. Reynolds, featuring the friendly Mr. Butts. "Believe me, there's nothing cooler than a 15-year-old walking down the street with a cigarette! Here, try one!" It's funny enough, but what endures is Mike's anguish at his complicity in this outrage. And outrage it is. Sure, Doonesbury is reliably funny, amazingly so under the circumstances. (Forty years …) But the ballast, unspoken but ever-present, is Trudeau's fearless outrage at the wrongs in the world. This is a guy who devoted a full Sunday strip to a father talking to his son who is dying of AIDS in a hospital.
Mike often figures in my favorite Doonesbury tic: the wordless third panel. It's a pause, a beat, where you know the characters so well that you don't need to be told what they're thinking. (See an example of the third-panel beat here.) When it's Mike, you know it's a sensible, if overwhelmed, reaction to the chaos around him. He'll try something and probably fail. Mike's life (all life?) is damage control. And so Mike, like the rest of us, beats on, leaky boat against the current, borne back ceaselessly into the past.
(Check out the strip where Mike becomes a Republican.)